Development and phenology of Ecklonia radiata at two depths in Goat Island Bay, New Zealand

E. radiata (C. Ag.) J. Ag. growing in Goat Island Bay, New Zealand produced up to 6 kg dry weight of tissue m super(-2) yr super(-1) in dense populations at 7-m depth. Half this tissue and an unknown amount of exudates were sloughed or torn off. Tissue production at 15 m was 0.3 to 0.5 kg m super(-2) yr super(-1). At this depth the plants grew only half as fast as in shallow water and the population density was decreased. Approximately 20% by weight of tissue produced at 7 m and 10% of that at 15 m was reproductive tissue. At both depths the elongation rate and percentage of water in stipes varied with stipe size. Initial sorus formation was related to plant size and not to age. Seasonal fluctuations in growth rate, haptera formation, frond size and sporulation were delayed in plants in deeper water.